Metal-air cells with minimal air access

ABSTRACT

A battery includes an air cathode, an anode, an aqueous electrolyte, and a housing, wherein, the housing includes one or more air access ports defining a total vent area, the battery exhibit a current density, a ratio of current density to total vent area is greater than about 100 mA/mm 2 , and the aqueous electrolyte comprises an amphoteric fluorosurfactant.

FIELD

The present technology is generally related to the field of metal-airbatteries and the uses thereof.

SUMMARY

In one aspect, a battery is provided that includes an air cathode, ananode, an aqueous electrolyte, and a housing, wherein: the housingcomprises one or more air access ports defining a total vent area; thebattery exhibit a cell limiting current at 1.15V; a ratio of celllimiting current at 1.15 V to total vent area is greater than about 100mA/mm²; and the aqueous electrolyte comprises an amphotericfluorosurfactant. In some embodiments, the ratio is greater than about150 mA/mm². In some embodiments, the ratio is greater than 250 mA/mm².In some embodiments, the ratio is from about 70 mA/mm² to about 1000mA/mm². In some embodiments, the battery has a nominal diameter of about8 mm and a nominal height of about 5.4 mm. In some embodiments, thebattery has a nominal diameter of about 8 mm and a nominal height ofabout 3.6 mm. In some embodiments, the battery has a nominal externalvolume from about 180 mm³ to about 270 mm³. In some embodiments, thebattery has a nominal electrode interfacial area is about 35 mm². Insome embodiments, the battery has a nominal electrode interfacial areafrom about 25 to 50 mm². In some embodiments, the total vent area isfrom about 0.030 mm² to about 0.115 mm². In some embodiments, the celllimiting current at 1.15 V is about 4 mA to about 15 mA.

In another aspect, a battery is provided comprising an air cathode, ananode, an aqueous electrolyte, and a housing, wherein: the housingcomprises one or more air access ports defining a total vent area; thebattery has an interfacial surface area between the anode and cathode; aratio of vent area to interfacial area is about 3×10⁻³ or smaller(provided that when the battery is a size 13 battery then the ratio isabout 2.4×10⁻³ or smaller); and the aqueous electrolyte comprises anamphoteric fluorosurfactant. In some embodiments, the ratio is fromabout 1.0×10⁻³ to about 3.0×10⁻³. In some embodiments, the ratio is fromabout about 1.0×10⁻³ to about 2.4×10⁻³. In some embodiments, the ratiois from about about 1.4×10⁻³ to about 3.0×10⁻³. In some embodiments, thebattery has a nominal diameter of about 8 mm and a nominal height ofabout 5.4 mm. In some embodiments, the battery has a nominal diameter ofabout 8 mm and a nominal height of about 3.6 mm. In some embodiments,the battery has a nominal external volume from about 180 mm³ to about270 mm³. In some embodiments, the battery has a nominal electrodeinterfacial area is from about 25 to 50 mm². In some embodiments, atotal vent area is from about 0.030 mm² to about 0.115 mm².

In a further aspect, a battery is provided comprising an air cathode, ananode, an aqueous electrolyte, and a housing, wherein: the housingcomprises one or more air access ports defining a total vent area; thebattery exhibits a cell limiting current at 0.9V and a cell limitingcurrent at 1.15V; the ratio of cell limiting current at 1.15 V to celllimiting current at 0.9V is greater than about 0.6; and the aqueouselectrolyte comprises an amphoteric fluorosurfactant. In someembodiments, the ratio is greater than about 0.7. In some embodiments,the ratio is greater than 0.75. In some embodiments, the ratio is fromabout 0.6 to 0.9. In some embodiments, the battery has a nominaldiameter of about 8 mm and a nominal height of about 5.4 mm. In someembodiments, the battery has a nominal diameter of about 8 mm and anominal height of about 3.6 mm. In some embodiments, the battery has anominal external volume from about 180 mm³ to about 270 mm³. In someembodiments, the nominal electrode interfacial area is about 35 mm². Insome embodiments, the total vent area is from about 0.030 mm² to about0.13 mm². In some embodiments, the cell limiting current at 1.15 V isabout 4 mA to about 15 mA.

In yet another aspect, a battery is provided comprising an air cathode,an anode, an aqueous electrolyte, and a housing, wherein: the housingcomprises one or more air access ports defining a total vent area; thebattery exhibits a cell limiting current at 0.9V; the battery, whendischarged at a current equal to half of the limiting current, maintainsvoltage of 1.17V or higher through 50% of its discharge to 0.9V; and theaqueous electrolyte comprises an amphoteric fluorosurfactant.

In yet a further aspect, a battery is provided, the battery comprisingan air cathode, an anode, an aqueous electrolyte, and a housing,wherein: the housing comprises one or more air access ports defining atotal vent area; the battery exhibits a cell limiting current at 0.9V;the battery, when discharged at a current equal to one-third of thelimiting current, maintains voltage of 1.20V or higher through 50% ofits discharge to 0.9V; and the aqueous electrolyte comprises anamphoteric fluorosurfactant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional, schematic view depicting an illustrativeelectrochemical cell.

FIG. 2 is a boxplot of capacity data for an embodiment of size 13 cellsof the present technology versus a comparative “standard” celldischarged according to the ANSI/IEC test 10/2 mA at 80% RH (relativehumidity), according to the working examples.

FIG. 3 is a boxplot of capacity data for an embodiment of size 312 cellsof the present technology versus a comparative “standard” celldischarged according to the ANSI/IEC test 10/2 mA at 80% RH (relativehumidity), according to the working examples.

FIG. 4 is a boxplot of capacity data for an embodiment of size 312 cellsof the present technology versus a comparative “standard” celldischarged according to the ANSI/IEC test 10/2 mA at 20% RH (relativehumidity), according to the working examples.

FIG. 5 is a plot of the potential versus a pure zinc reference when acurrent draw of 1 mA/cm² and 5 mA/cm² was applied to the cathode of ametal-air cell employing three different electrolytes, according to theexamples.

FIG. 6 is a plot of the ratio of the limiting current at 1.15V to thelimiting current at 0.9V for cells according to the present application(left) v. commercial cells (right), according to the working examples.

FIG. 7 is a scatterplot of limiting current at 1.15V vs. limitingcurrent at 0.9V for cells according to the present application (darkdots) and commercial cells (hollow diamond shapes), according to theworking examples.

FIG. 8 is a set of discharge curves at constant currents for two size 13cells according to the present application and one commercial cell forreference, showing the closed circuit voltage during discharge (V) vs.the capacity (mAh). Refer to example 8.

FIG. 9 is a set of discharge curves at constant currents for two size 13cells according to the present application and one commercial cell forreference, showing the closed circuit voltage during discharge (V) vs.the capacity (mAh). Refer to example 8.

FIG. 10 is a boxplot of capacity data for an embodiment of size 312cells of the present technology with three different total vent areas inthe range of 0.0330 mm² to 0.0869 mm² discharged according to theANSI/IEC test 10/2 mA at 50% RH (relative humidity), according to theworking examples.

FIG. 11 is a boxplot of capacity data for an embodiment of size 312cells of the present technology with three different total vent areas inthe range of 0.0330 mm² to 0.0869 mm² discharged according to theANSI/IEC test 5/2 mA at 50% RH (relative humidity), according to theworking examples.

FIG. 12 is a boxplot of capacity data for an embodiment of size 13 cellsof the present technology with three different total vent areas in therange of 0.0499 mm² to 0.1295 mm² discharged according to the ANSI/IECtest 12/3 mA at 50% RH (relative humidity), according to the workingexamples.

DETAILED DESCRIPTION

Various embodiments are described hereinafter. It should be noted thatthe specific embodiments are not intended as an exhaustive descriptionor as a limitation to the broader aspects discussed herein. One aspectdescribed in conjunction with a particular embodiment is not necessarilylimited to that embodiment and can be practiced with any otherembodiment(s).

As used herein, “about” will be understood by persons of ordinary skillin the art and will vary to some extent depending upon the context inwhich it is used. If there are uses of the term which are not clear topersons of ordinary skill in the art, given the context in which it isused, “about” will mean up to plus or minus 10% of the particularterm—for example, “about 10 wt. %” would be understood to mean “9 wt. %to 11 wt. %.” It is to be understood that when “about” precedes a term,the term is to be construed as disclosing “about” the term as well asthe term without modification by “about”—for example, “about 10 wt. %”discloses “9 wt. % to 11 wt. %” as well as disclosing “10 wt. %.”

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the elements (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. Recitation of ranges of values herein are merely intended toserve as a shorthand method of referring individually to each separatevalue falling within the range, unless otherwise indicated herein, andeach separate value is incorporated into the specification as if it wereindividually recited herein. All methods described herein can beperformed in any suitable order unless otherwise indicated herein orotherwise clearly contradicted by context. The use of any and allexamples, or exemplary language (e.g., “such as”) provided herein, isintended merely to better illuminate the embodiments and does not pose alimitation on the scope of the claims unless otherwise stated. Nolanguage in the specification should be construed as indicating anynon-claimed element as essential.

In general, “substituted” refers to an alkyl, alkenyl, alkynyl, aryl, orether group, as defined below (e.g., an alkyl group) in which one ormore bonds to a hydrogen atom contained therein are replaced by a bondto non-hydrogen or non-carbon atoms. Substituted groups also includegroups in which one or more bonds to a carbon(s) or hydrogen(s) atom arereplaced by one or more bonds, including double or triple bonds, to aheteroatom. Thus, a substituted group will be substituted with one ormore substituents, unless otherwise specified. In some embodiments, asubstituted group is substituted with 1, 2, 3, 4, 5, or 6 substituents.Examples of substituent groups include: halogens (i.e., F, Cl, Br, andI); hydroxyls; alkoxy, alkenoxy, alkynoxy, aryloxy, aralkyloxy,heterocyclyloxy, and heterocyclylalkoxy groups; carbonyls (oxo);carboxyls; esters; urethanes; oximes; hydroxylamines; alkoxyamines;aralkoxyamines; thiols; sulfides; sulfoxides; sulfones; sulfonyls;sulfonamides; amines; N-oxides; hydrazines; hydrazides; hydrazones;azides; amides; ureas; amidines; guanidines; enamines; imides;isocyanates; isothiocyanates; cyanates; thiocyanates; imines; nitrogroups; nitriles (i.e., CN); and the like.

As used herein, “alkyl” groups include straight chain and branched alkylgroups having from 1 to about 20 carbon atoms, and typically from 1 to12 carbons or, in some embodiments, from 1 to 8 carbon atoms. Alkylgroups may be substituted or unsubstituted. Examples of straight chainalkyl groups include methyl, ethyl, n-propyl, n-butyl, n-pentyl,n-hexyl, n-heptyl, and n-octyl groups. Examples of branched alkyl groupsinclude, but are not limited to, isopropyl, sec-butyl, t-butyl,neopentyl, and isopentyl groups. Representative substituted alkyl groupsmay be substituted one or more times with, for example, amino, thio,hydroxy, cyano, alkoxy, and/or halo groups such as F, Cl, Br, and Igroups. As used herein the term haloalkyl is an alkyl group having oneor more halo groups. In some embodiments, haloalkyl refers to aper-haloalkyl group.

Cycloalkyl groups are cyclic alkyl groups such as, but not limited to,cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, andcyclooctyl groups. In some embodiments, the cycloalkyl group has 3 to 8ring members, whereas in other embodiments the number of ring carbonatoms range from 3 to 5, 6, or 7. Cycloalkyl groups may be substitutedor unsubstituted. Cycloalkyl groups further include polycycliccycloalkyl groups such as, but not limited to, norbornyl, adamantyl,bornyl, camphenyl, isocamphenyl, and carenyl groups, and fused ringssuch as, but not limited to, decalinyl, and the like. Cycloalkyl groupsalso include rings that are substituted with straight or branched chainalkyl groups as defined above. Representative substituted cycloalkylgroups may be mono-substituted or substituted more than once, such as,but not limited to: 2,2-; 2,3-; 2,4-; 2,5-; or 2,6-disubstitutedcyclohexyl groups or mono-, di-, or tri-substituted norbornyl orcycloheptyl groups, which may be substituted with, for example, alkyl,alkoxy, amino, thio, hydroxy, cyano, and/or halo groups.

Alkenyl groups are straight chain, branched or cyclic alkyl groupshaving 2 to about 20 carbon atoms, and further including at least onedouble bond. In some embodiments alkenyl groups have from 1 to 12carbons, or, typically, from 1 to 8 carbon atoms. Alkenyl groups may besubstituted or unsubstituted. Alkenyl groups include, for instance,vinyl, propenyl, 2-butenyl, 3-butenyl, isobutenyl, cyclohexenyl,cyclopentenyl, cyclohexadienyl, butadienyl, pentadienyl, and hexadienylgroups among others. Alkenyl groups may be substituted similarly toalkyl groups. Divalent alkenyl groups, i.e., alkenyl groups with twopoints of attachment, include, but are not limited to, CH—CH═CH₂, C═CH₂,or C═CHCH₃.

The term “alkoxy group” refers to a hydroxy group (OH) in which the Hhas been replaced by an alkyl group comprising from 1 to 12 carbon atomsas defined herein. In some embodiments, the alkoxy group comprises 1 to7 or 1 to 4 carbon atoms. The alkoxy group may be, e.g., a methoxygroup, an ethoxy group, a propoxy group, a isopropoxy group, a n-butoxygroup, a sec-butoxy group, tert-butoxy group, pentoxy group, isopentoxygroup, 3-methylbutoxy group, 2,2-dimethylpropoxy group, n-hexoxy group,2-methylpentoxy group, 2,2-dimethylbutoxy group, 2,3-dimethylbutoxygroup, n-heptoxy group, 2-methylhexoxy group, 2,2-dimethylpentoxy group,2,3-dimethylpentoxy group, cyclopropoxy group, cyclobutoxy group,cyclopentyloxy group, cyclohexyloxy group, cycloheptyloxy group,1-methylcyclopropyl oxy group and others. In some embodiments, thealkoxy group comprises O—C₁-C₆-alkyl groups. In other embodiments, thealkoxy group comprises O—C₁-C₄-alkyl groups.

The term “amine” (or “amino”) as used herein refers to —NR¹⁰⁰R¹⁰¹groups, wherein R¹⁰⁰ and R¹⁰¹ are independently hydrogen, or asubstituted or unsubstituted alkyl, alkenyl, alkynyl, cycloalkyl, aryl,aralkyl, heterocyclylalkyl or heterocyclyl group as defined herein. Insome embodiments, the amine is alkylamino, dialkylamino, arylamino, oralkylarylamino. In other embodiments, the amine is NH₂, methylamino,dimethylamino, ethylamino, diethylamino, propylamino, isopropylamino,phenylamino, or benzylamino.

The term “halogen” or “halo” as used herein refers to bromine, chlorine,fluorine, or iodine. In some embodiments, the halogen is fluorine. Inother embodiments, the halogen is chlorine or bromine.

The term “hydroxyl” as used herein can refer to —OH or its ionized form,—O—.

The term “nitrile” or “cyano” as used herein refers to the —CN group.

The term “thio” as used herein refers to a —S— group or an ether whereinthe oxygen is replaced with sulfur.

As used herein, the term “amphoteric fluorosurfactants” refers tofluorosurfactants including at least one cationic group and/or groupable to be protonated into a cationic group, such as a primary,secondary, tertiary, and/or quaternary amine group; and at least oneanionic group and/or group able to be deprotonated into an anionicgroup, such as a carboxy group, a sulfonic acid group, phosphate group,a phosphonate group, are a salt of any one or more thereof.

As used herein, the term “betaine functionality” refers to a neutralcompound with a positively charged cationic functional group and anegatively charged functional group. In some embodiments, the cationicfunctional group may be a quaternary ammonium or phosphonium cation,which bears no hydrogen atom. In some embodiments, the negativelycharged functional group may be a carboxylate group.

As used herein, the term “short-chain perfluoro substituent” refers to aC₁-C₇ perfluoro substituent.

As used herein, the term “zinc anode” refers to an anode that includeszinc as an anode active material.

As used herein, the term “ppm” means parts per million by weight, unlessexplicitly expressed otherwise.

As used herein, the term “ppm” as regards amphoteric fluorosurfactantsmeans parts per million by weight of active component, unless explicitlyexpressed otherwise.

In the design of metal-air cells, it is useful to define properties ofthe cell in terms of limiting current. A cell limiting current test isperformed by holding the cell at a specific voltage for a specificamount of time, and measuring the resulting current provided by the cellat a set time endpoint. As a cell is initially held to a voltage (usingan instrument that adjusts the current drain from the cell to reach theset voltage), the current will initially be high, and declineasymptotically to a relatively constant level. Typically, the set timeis chosen at a point where the current is in this relatively constantrange.

As used herein, “cell limiting current at 0.9V” means the currentprovided by a metal-air electrochemical cell at 0.9V, at the end of 60seconds during which the cell has been held at a voltage of 0.9V. Priorto this test, the cell should not be under any load for at least 60seconds.

As used herein, “cell limiting current at 1.15V” means the currentprovided by a metal-air electrochemical cell at 1.15V, at the end of 60seconds during which the cell has been held at a voltage of 1.15V. Priorto this test, the cell should not be under any load for at least 60seconds.

It has now been observed that oxygen utilization in a metal-airelectrochemical cell may be unexpectedly improved through thecombination of an electrolyte having a fluorinated amphoteric surfactantand lithium hydroxide in a cell housing having limited air access. Theelectrolyte formulation has been found to increase closed cell voltageand cathode half-cell voltage, while allowing for reduction in oxygenaccess required by the cell for a given current draw and/or maintaininga desirable closed circuit voltage. This greater efficiency in oxygenutilization and higher cell voltage enables the use of a smaller ventarea to the exterior of the cell, reducing exposure to the detrimentaleffects of moisture (H₂O vapor) and carbon dioxide (CO₂). This greaterefficiency in oxygen utilization and higher cell voltage also enablesthe use of less porous diffusion layers between the air access ports andthe active cathode material, also reducing exposure to the detrimentaleffects of moisture and CO₂. These changes reduce the access to oxygenand improve performance at low and high humidity conditions as well asenvironments with elevated CO₂ concentrations.

Described herein is the combination of a high voltage anode formulationcomposed of an amphoteric fluorosurfactant and a cell designed such thatthe cell limiting current is reduced to the lowest possible level whilestill meeting the drain rate use requirements. The present technologyprovides a battery that includes an air cathode, an anode, an aqueouselectrolyte that includes an amphoteric surfactant, and a housing thatincludes one or more air access ports defining a total area of voidspace (“vent area”). The ratio of a number of the variables to the ventarea has been tested for a variety of cells.

In accordance with the surprising observations described herein, when anamphoteric fluorosurfactant is used in the electrolyte of the batteriesof the present technology, the minimum required total vent area definedby the air access ports was found to be surprisingly low. By way ofexample, in the improved batteries of the present technology the totalvent area of a size 312 cell may be 0.0660 mm², a 24% reduction from thestandard/convention dimension of 0.0869 mm². In some embodiments, thesize 312 vent area may be 0.033 mm². In some embodiments, the size 312vent area may be from about 0.01 mm² to about 0.1 mm², or from about0.03 mm² to about 0.07 mm². As another example, in the improvedbatteries of the present technology the total vent area of size 13 cellmay be 0.0998 mm², a 30% reduction from the reduced from thestandard/convention dimension of 0.1295 mm². In some embodiments, thesize 13 vent area may be 0.1295 mm², or about 0.0499 mm². In someembodiments, the size 13 vent area may be from about 0.04 mm² to about0.15 mm², or about 0.05 mm² to about 0.13 mm², or from about 0.09 mm² toabout 0.13 mm². Without being bound by theory, it is proposed that thereduced vent area is made possible by the high voltage and moreefficient electrolyte formulation (i.e., including an amphotericfluorosurfactant and optionally LiOH.xH₂O) where the amphotericfluorosurfactant may help reduce voltage suppression while maintaininggassing reliability and the combination of the components in the anodemay provide for a significantly enhanced improvement in cell voltage andcell performance.

As a point of reference, a size 13 cell has outer dimensions of about8.0 mm in diameter and about 5.4 mm in height, while a size 312 cell hasouter dimensions of about 8.0 mm in diameter and about 3.6 mm in height.These are nominal dimensions and typical actual dimensions are 0 to 0.2mm smaller than the nominals. The external volume is calculated here,and shown in Table 1 below, as if the cell were a cylinder at nominaldimensions, although the actual cell volumes may be slightly less bothdue to deviations in actual dimensions for each cell produced, and toone end of the cell incorporating a notch to prevent backwards insertionof such small devices. Electrode interfacial areas are calculated basedon the diameter of the hole through the insulator (6.7 mm) on the insideof the cell.

TABLE 1 Illustrative Cell dimensions for new invention Insulator throughNominal hole Nominal Nominal Nominal external inside electrode CellDiameter Height volume diameter interfacial Size (mm) (mm) (mm³) (mm)area (mm²) 312 8.0    3.6 180  6.706 35.32   13 8.0    5.4 270  6.72535.52  Typical cell limiting current at Cell Typical 1.15 V for limitingcell invention current limiting (mA) [called at 1.15 current at currentV/cell Vent Vent area/ 0.9 V for density for limiting area interfacialinvention internal current Size (mm²) area (mA) testing] at 0.9 V 3120.0660 1.87 × 10⁻³  12 10      0.833  13 0.0998 2.81 × 10⁻³  13 10     0.769

As noted above, the dimensions provided are approximate, and they mayrange from their nominal values to their actual values. Accordingly, wenote that the external volumes that may be calculated may range for acell from about 150 mm³ to about 300 mm³. Further, the interfacial areasof some cells may vary for a number of reasons including variation inexact thickness of the cell housing, the actual diameter of the cellinsulators, and the like. Thus, the interfacial area may range fromabout 25 mm² to about 50 mm². More broadly, interfacial area of similarformat cells range from 15 to 75 mm².

The cell limiting current of the cells at 1.15 V is dependent upon thecell design. The design factors that affect this element include but arenot limited to the vent area of the cell, the diffusion layer porositybetween the air access ports and the cathode active layer, and theelectrolyte and anode elements. Ultimately, these design elements willaffect the ability of the cell to access and utilize oxygen efficiently.Thus, the ratio of limiting current at 1.15 V to vent area will providea measure of those abilities no matter the size of the cell. Accordingto various embodiments, a cell may be provided in which a ratio oflimiting current at 1.15 V to vent area is greater than 100 mA/mm². Insome embodiments, this ratio may be greater than about 150 mA/mm²,greater than 200 mA/mm², greater than 210 mA/mm², or greater than 250mA/mm². In other embodiments, this ratio may be from about 10 mA/mm² toabout 1000 mA/mm², from about 80 mA/mm² to about 500 mA/mm², from about70 mA/mm² to about 300 mA/mm², from about 70 mA/mm² to about 220 mA/mm²,or from about 100 mA/mm² to about 200 mA/mm².

Another measure of electrode capacity is found in the relationshipbetween the vent area and the interfacial area, the area between theanode and cathode. The ratio of these values provides a measure of therelative area of the air access ports that allow air access to thecathode, as compared to the amount of electrode interface that couplesthe activity of the cathode to the electrolyte and anode electrochemicalreaction. Without being bound by theory, the ratio of vent area tointerfacial area indicates the relative kinetic properties of thetransport of oxygen into the cell vs. the activation and transport ofthe oxygen and incorporation into the electrolyte for use with theanode, as dictated by the properties of the triple phase boundary at thecathode-anode interface. The interfacial area is a rough estimate of theamount of triple phase boundary required, assuming volume, tortuosityand wettability are constant. If the vent area required is small, lessoxygen enters the cell and less is available for conversion to hydroxylgroups and oxygen ions in the electrolyte. The assumption is that theoverpotential for the reaction on the anode must therefore be smaller asless excess reactant is required in the electrolyte. Alternatively,there could be a higher activity at the cathode sites to convert intoreactants in the electrolyte. The ratio of vent area to interfacial areamay be about 1.0×10⁻⁴ or greater, or about 1.0×10⁻⁴ or greater. Theratio of vent area to interfacial area may be from about 1.0×10⁻⁴ toabout 3.0×10⁻³. The ratio of vent area to interfacial area may be fromabout 1.0×10⁻³ to about 3.0×10⁻³. In various embodiments, the ratio ofvent area to interfacial area may be from about about 1.0×10⁻³ to about3.0×10⁻³, from about about 1.0×10⁻³ to about 2.4×10⁻³, or from aboutabout 1.4×10⁻³ to about 3.0×10⁻³.

Further measures of cell activity and stability may be found bymeasuring the ratio of cell limiting current at 1.15 V to cell limitingcurrent at 0.9 V. The cell limiting current at 1.15 V represents themaximum current that can be generated by the cell at 1.15 V, which is areasonable voltage in the operating window of a hearing aid device. Thecell limiting current at 0.9 V represents the maximum current at thelowest reasonable operating voltage this battery should see. The 0.9 Vcell limiting voltage represents kinetic phenomenon far fromequilibrium. B y studying the ratio of these two values, it is possibleobserve that different rate limiting steps and mechanisms are at play atthese two potentials as dictated by the battery design. According tovarious embodiments, a cell may be provided in which a ratio of celllimiting current at 1.15 V to cell limiting current at 0.9 V is greaterabout 0.6. In some embodiments, this ratio may be greater than about 0.7or greater than 0.75. In other embodiments, this ratio may be from about0.6 to 0.9.

The cell limiting current at 0.9V also indicates the current the cell isable to provide when the current becomes limited by the availability ofoxygen to the cathode. This current is “limiting” in two senses: one,because the current changes little with time after an initialapproximately 30 seconds when the cell is held at 0.9V (theelectrochemical definition), but also, second, because a furtherreduction in voltage below 0.9V results in little change in current duethe position of this voltage on the cell's polarization curve. In thedesign of the cell for a specific application, choices are made in thesize and number of air access ports, and the porosity of other layers ofmaterial that oxygen must diffuse through to reach the reaction site.The cell must have adequate limiting current to support the desireddischarge current range of the cell when in use. However, if thelimiting current at 0.9V is any higher than needed, the cell isadversely affected. This adverse effect is because moisture (H₂O vapor)and carbon dioxide (CO₂) have very similar diffusion characteristicsthrough air access ports and membrane layers. Thus, higher limitingcurrent at 0.9V serves as a proxy for more diffusion of water vapor andcarbon dioxide. Diffusion of water vapor in or out of the cell willoccur whenever the cell is not in an environment with equilibriumhumidity, and will change the makeup of the cell and adversely affectits performance. Likewise, carbon dioxide is known to dissolve in theelectrolyte, reduce ionic conductivity, and reduce the cell performance.Thus, it is desirable for the cell to have the lowest limiting currentat 0.9V possible while supporting the desired discharge current rates.

The limiting current measured at 1.15V, as referred to earlier, is anapproximation of the highest usable constant current load for the cell,because this is measured at a working voltage for the cell. It isnoteworthy that this measurement is only “limiting” in time, but it issensitive to small changes in voltage, unlike the limiting currentmeasured at 0.9V, because it is on a rather flat part of thepolarization curve where small changes in voltage result in largechanges in current. Therefore, a cell with a higher ratio of limitingcurrent at 1.15V to limiting current at 0.9V is advantageous, because itcan be designed to provide the same current under device workingconditions as an ordinary cell, while having a lower limiting current at0.9V, and, therefore, lower moisture and carbon dioxide transport.

It has now been found that with the cells described herein, a continuouscurrent may be provided while the cell has a lower limiting current at0.9V, than previously required. A limiting current at 0.9V of only twicethe continuous current is required. Thus, for 6 mA current, only 12 mAlimiting current at 0.9V is required, and this cell provides superiorresults because of the reduction in moisture and carbon dioxidetransport.

The above rule could be modified depending on the voltage requirementand current pulse requirements of the application, but the generalprinciple and differences in the designs still applies. For an ordinarycell, if a limiting current at 0.9V that is twice the maximum continuouscurrent required is adequate, then with the invented cell, a limitingcurrent at 0.9V of only 1.33 times the continuous current would beequally adequate. In this case, if the continuous current demanded is 9mA, an ordinary cell would need to be designed with limiting current at0.9V of 18 mA, but the invented cell could be designed with limitingcurrent at 0.9V of 12 mA.

In any embodiment herein, the amphoteric fluorosurfactant may include ashort-chain perfluoro substituent, which cannot break down toperfluorooctanoic acid. In any embodiment herein, the amphotericfluorosurfactant may include a betaine functionality. For example, theamphoteric fluorosurfactant may be represented as a compound of Formula(I):

wherein R¹, R², R³, R⁴, R⁵, R⁶, R⁷, and R⁸ are each independently ahydrogen, alkyl, alkenyl, or cycloalkyl group; X¹ is —C(O)—, —SO₂—,—C(O)NR^(a)—, —SO₂NR^(a)—, —CO₂—, or —SO₂O—; R^(a) is H or an alkylgroup; m and p are each independently 0, 1, 2, 3, 4, 5, or 6; and n andr are each independently 1, 2, 3, 4, or 5. In some embodiments, R¹-R⁶are H, R⁷ and R⁸ are C₁-C₄ alkyl, n and p are 2, m is from 4, 5, or 6,X¹ is SO₂; and r is 1.

In any embodiment herein, the amphoteric fluorosurfactant may be presentin the electrolyte from about 200 ppm to about 20,000 ppm. Thus, in anyembodiment herein, the electrolyte may include the amphotericfluorosurfactant in an amount of about 500 ppm, about 600 ppm, about 700ppm, about 800 ppm, about 900 ppm, about 1,000 ppm, about 2,000 ppm,about 3,000 ppm, about 4,000 ppm, about 5,000 ppm, about 6,000 ppm,about 7,000 ppm, about 8,000 ppm, about 9,000 ppm, about 10,000 ppm,about 11,000 ppm, about 12,000 ppm, about 13,000 ppm, about 14,000 ppm,about 15,000 ppm, about 16,000 ppm, about 17,000 ppm, about 18,000 ppm,about 19,000 ppm, about 20,000 ppm, or ranges between any two of thesevalues (including endpoints). For example, in any embodiment herein, theamphoteric fluorosurfactant may be present in the electrolyte from about2000 ppm to about 15000 ppm or from about 3000 ppm to about 12000 ppm.By way of another example, in any embodiment herein, it may be theamphoteric fluorosurfactant concentration in the electrolyte is about10,000 ppm.

The battery may be configured in accordance or consistent with metal-airbattery cell designs, such as zinc/silver oxide batteries,zinc/manganese dioxide batteries, etc. For example, the battery may bedesigned to specifications suitable for a metal-air button size battery.Further, the shape of the battery may such that the anode is held in asomewhat flat or pan-shaped position.

Hereafter, disclosure via references to FIG. 1 is provided to aid inunderstanding but is not intended mandate the inclusion of the describedfeatures in metal-air batteries of the present technology. However, inany embodiment of the present disclosure, the battery of the presentdisclosure may be as illustrated in FIG. 1 . FIG. 1 illustrates that incell 10 of the battery, the negative electrode contains the anode canassembly 22, with an anode can 24 including an electrochemicallyreactive anode 26, contained therein and an insulating gasket 60. Theanode can 24 has a base wall 28, and circumferentialdownwardly-depending side wall 30. Side walls 30 terminate in acircumferential can foot 36. The base wall and side walls 30 generallydefine the anode cavity 38 within the anode can 24, which cavitycontains the anode 26.

The anode can 24 may include an alloy of copper, which includes copperand metals such as aluminum, silicon, cobalt, tin, chromium, zinc, andmixtures of any two or more thereof. For example, in any embodimentdisclosed herein, the entire anode can 24 may include an alloy ofcopper.

The cathode 42 comprises the area from below the separator 74 to thecathode can 44. This cathode 42 area includes the porous diffusion layer57, the cellulose air diffusion layer and the cathode active layer 72.Cathode can 44 has a bottom 46, and a circumferential upstanding sidewall 47. Bottom 46 has a generally flat inner surface 48, a generallyflat outer surface 50, and an outer perimeter 52 defined on the flatouter surface 50. A plurality of air access ports 54 extend through thebottom 46 of the cathode can 44, providing avenues for traverse ofoxygen through the bottom 46 into the adjacent cathode can assembly 40.An air reservoir 55 spaces the cathode can assembly 40 from bottom 46and the corresponding air access ports 54. A porous diffusion layer 57and a cellulose air diffusion layer 32 fill the air reservoir 55. Sidewall 47 of the cathode can has an inner surface 56 and an outer surface58.

As noted above, the air access ports 54 define the vent areas throughwhich oxygen may pass into the cell forming a voltaic cell with zincgenerating an electric current. In accordance with the surprisingobservations described herein, when an amphoteric fluorosurfactant isused in the electrolyte of the batteries of the present technology, theminimum required total vent area defined by the air access ports 54 wasfound to be surprisingly low. As discussed earlier, where the metal-airbattery is a size 13 cell the total vent area defined by all of the airaccess ports in the housing is from about 0.05 mm² to about 0.1995 mm².Thus, in any embodiment disclosed herein of a size 13 cell, the totalvent area defined by all of the air access ports may be from about 0.05mm² to about 0.10 mm², from about 0.06 mm² to about 0.095 mm², fromabout 0.06 mm² to about 0.085 mm², from about 0.07 mm² to about 0.09mm², or from about 0.08 mm² to about 0.085 mm².

The anode can assembly 22 is electrically insulated from the cathode canassembly 40 by an insulating gasket 60. Insulating gasket 60 includes acircumferential side wall 62 disposed between the upstanding side wall47 of the cathode can and the downwardly-depending side wall 30 of theanode can. An insulating gasket foot 64 is disposed generally betweenthe can foot 36 of the anode can and the cathode can assembly 40. Aninsulating gasket top 66 is positioned at the locus where the side wall62 of insulating gasket 60 extends from between the side walls 30 and 47adjacent the top of the cell.

The outer surface 68 of the cell 10 is thus defined by portions of theouter surface of the top of the anode can 24, outer surface 58 of theside wall 47 of the cathode can 44, outer surface 50 of the bottom ofthe cathode can 44, and the top 66 of the insulating gasket 60.

The insulating gasket 60 performs at least two primary functions. First,the insulating gasket 60 serves as a closure for the cell 10, to preventanode 26 and/or electrolyte from leaking from the cell between the outersurface of the side wall of the anode can 30 and the inner surface 56 ofthe side wall of the cathode can 47. Thus, the insulating gasket 60 mustpossess adequate liquid sealing properties to prevent such leakage.Generally, such properties are available in a variety of resilientlydeformable thermoplastic polymeric materials.

Second, the insulating gasket 60 provides electrical insulation,preventing all effective direct electrical contact between the anode can24 and the cathode can 44. Accordingly, the side wall 62 of theinsulating gasket 60 must circumscribe, and provide electricalinsulation properties about, the entirety of the circumference of thebattery between outer surface and inner surface 56, generally from thetop of side wall 47 to the bottom of side wall 30. Similarly, the foot64 of the insulating gasket 60 must circumscribe, and provide electricalinsulation properties about, the entirety of the circumference of thecell between foot 36 of side wall 30, the lower portion of side wall 47,and the outer perimeter portion of the cathode can assembly 40. Thecombination of good liquid sealing properties and good electricalinsulation properties is typically achieved by molding knownbattery-grade nylon polymeric material in the desired configuration.

In order to meet the electrical insulation requirements, the insulatinggasket 60 may have good dielectric insulation properties, may have aminimum thickness about side wall 62, and may be free of any pinholes orother imperfections that might permit transmission of electric currentbetween side walls 30 and 47. Thickness for the insulating gasket sidewall 62 of about 200 to about 250 microns are common in conventionalelectrochemical cells. Thickness as thin as 100 microns are found inhigher-performing cells and are acceptable for cells of the disclosure,using the same resiliently deformable thermoplastic nylon material asthe thicker insulating gaskets of the conventional art

Depending on the structure of the battery to which the insulating gasketis to be applied, intermediate thicknesses such as, e.g., 150 microns,140 microns, 127 microns, or the like, may be selected for some cells.However, where cell volume efficiency is a driving consideration,preferred thicknesses are less, for example 120 microns or 110 micronsto as thin as 100 microns. Thus, the range of thicknesses for insulatinggaskets 60 preferred for use in cells 10 of the disclosure has a lowerend of about 100 microns. Other methods of insulation, potentially withstill thinner insulating materials, are possible and are notincompatible with the material disclosed here. [0066] It should be notedthat in this design, the inside diameter of the insulator defines theapproximate usable interfacial area between the anode and cathode.However, in other cell designs, a different component may control theinterfacial area, and yet the concept of interfacial area is equallyimportant in that case.

In any embodiment disclosed herein, it may be porous diffusion layer 57is a micro-porous hydrophobic polymeric material such as apolytetrafluoroethylene (PTFE) membrane about 25 to about 100 micronsthick, which permits passage of air therethrough and which is generallyimpervious to battery electrolyte. For example, the porous diffusionlayer 57 is Teflon™. In any embodiment disclosed herein, it may beporous diffusion layer 57, in combination with the air access ports 54,is used to efficiently transport oxygen to the active reaction surfacearea of the cathode assembly.

The cellulose air diffusion layer 32 may be located underneath theporous diffusion layer 57 and act as a protective lateral air diffusionlayer. Specifically, when the cell is activated, the anode can assembly22 presses down on the separator 74 and the cellulose air diffusionlayer 32 helps to protect the air access ports 54 from being completelycovered.

Active layer 72 may further include a connecting substratum, such as aconductive woven nickel wire layer (not shown), capable of interfacing,as a current collector, with the cathode can. In any embodimentdisclosed herein, carbon may form a matrix surrounding the conductivelayer of nickel wire. Nickel may be used for the conductive layerbecause nickel exhibits little or no corrosion in the environment of thezinc air cell, and also because nickel is an excellent electricalconductor. In any embodiment disclosed herein, the thickness of thecathode assembly between the separator 74 and the porous diffusion layer57 may be as small as possible.

The aqueous electrolyte for the metal-air batteries of the presenttechnology may include a base, such as sodium hydroxide (NaOH),potassium hydroxide (KOH), or a combination thereof. The electrolyte ofany embodiment disclosed herein may include a surfactant system, acorrosion inhibitor (e.g., one or more of indium hydroxide, polyaniline,polyethylene glycol, polypropylene glycol, and lithium hydroxide), agelling agent (e.g., polyacrylate polymer), gas suppressing additive(e.g., one or more of zinc oxide, aluminum hydroxide, LiOH, and calciumbromide), potassium hydroxide, sodium hydroxide, cesium hydroxide, boricacid, sodium borate, potassium borate, sodium stannate, potassiumstannate, or a combination of any two or more thereof.

The surfactant system may include at least one amphotericfluorosurfactant. For example, the surfactant system may include atleast two amphoteric fluorosurfactants. In any embodiment herein, it maybe the surfactant system includes one or more amphotericfluorosurfactants as well as one or more of a corrosion inhibitor (e.g.,one or more of indium hydroxide, polyaniline, polyethylene glycol,polypropylene glycol, and lithium hydroxide), a gelling agent (e.g.,polyacrylate polymer), gas suppressing additive (e.g., one or more ofzinc oxide, aluminum hydroxide, LiOH, and calcium bromide), potassiumhydroxide, sodium hydroxide, cesium hydroxide, boric acid, sodiumborate, potassium borate, sodium stannate, and potassium stannate. Inany embodiment disclosed herein, the surfactant system may beCHEMGUARD'S-111, CHEMGUARD'S-500, CAPSTONE® FS-50, CAPSTONE®FS-51,APFS-14, DYNAX DX3001, ZONYL® FSK, ZONYL® FS-500, or a combination ofany two or more thereof.

The electrolyte and/or surfactant system of any embodiment herein mayinclude an additional surfactant such as hexyl diphenyl oxide disulfonicacid, diethylenetriamine, octylphenoxypolyethoxyethanol, a compound ofFormula (III), or a combinations of any two or more thereof. Compoundsof Formula (III) include:

wherein R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰, and R²¹ are eachindependently a hydrogen, alkyl, alkenyl, or cycloalkyl group; X² is Oor S; X³ is OH or SH; and w is 5-50. In any embodiment disclosed herein,it may be that R¹³, R¹⁴, R¹⁵, R¹⁶, R¹⁷, R¹⁸, R¹⁹, R²⁰ and R²¹ are eachhydrogen. In any embodiment disclosed herein, it may be that X² is O. Inany embodiment disclosed herein, it may be that X³ is OH. In anyembodiment disclosed herein, it may be that w is 5-15. In any embodimentdisclosed herein, it may be that w is 5-10. In any embodiment disclosedherein, it may be that R¹³ is a C₁-C₁₂ alkyl group; R¹⁴, R¹⁵, R¹⁶, R¹⁷,R¹⁸, R¹⁹, R²⁰, and R²¹ are each hydrogen; X² is O; X³ is OH; and w is5-15. In any embodiment disclosed herein, it may be that R¹³ is octyland w is 5-10. In another embodiment, R¹³ is 1,1,3,3-tetramethylbutyland w is 5-10.

The electrolyte of any embodiment herein may further include a hexyldiphenyl oxide disulfonic acid as part of a hexyl diphenyl oxidedisulfonic acid surfactant system. The hexyl diphenyl oxide disulfonicacid surfactant system may reduce voltage suppression. The hexyldiphenyl oxide disulfonic acid surfactant system of any embodimentdisclosed herein may have a density of from about 9.0 to about 10.0lbs./gallon, such as a density of about 9.8 lbs./gallon. The hexyldiphenyl oxide disulfonic acid surfactant system of any embodimentdisclosed herein may have a pH of less than about 2.0. The hexyldiphenyl oxide disulfonic acid may have a solubility of about 50% inwater.

The hexyl diphenyl oxide disulfonic acid surfactant system of anyembodiment disclosed herein may include from about 70% to about 75%, byweight, of sulfonated benzene, 1,1′-oxybis-sec-hexyl derivatives. In anyembodiment herein, the hexyl diphenyl oxide disulfonic acid surfactantsystem may include from about 0% to about 5% or from about 2% to about4%, by weight, of sulfuric acid. The hexyl diphenyl oxide disulfonicacid surfactant of any embodiment disclosed herein may include fromabout 20% to about 30% or from about 22% to about 28%, by weight, ofwater. In an exemplary embodiment, the hexyl diphenyl oxide disulfonicacid surfactant is Calfax® 6LA-70, available from Pilot ChemicalCompany, 2744 East Kemper Road, Cincinnati, Ohio, 45241, where Calfax®6LA-70 may also act as a coupling agent and/or an HLB modifier in otherembodiments of the present disclosure. Thus, the term “surfactant” isnot to be seen in a limiting sense as illustrated for Calfax® 6LA-70,but instead the term is a description of one of the functions e.g., thathexyl diphenyl oxide disulfonic acids and/or hexyl diphenyl oxidedisulfonic acid surfactant systems may provide.

In any embodiment herein, it may be the hexyl diphenyl oxide disulfonicacid is included in an amount from about 500 ppm to about 5,000 ppm,such as from about 1,000 ppm to about 4,000 ppm or about 2,000 ppm toabout 3,000 ppm. Thus, the hexyl diphenyl oxide disulfonic acid may bepresent in an amount of about 1,000 ppm, about 2,000 ppm, about 3,000ppm, about 4,000 ppm, or about 5,000 ppm, or any range between any twoof these values (including endpoints). For example, the hexyl diphenyloxide disulfonic acid may be present in an amount of about 3,000 ppm; asanother example, the hexyl diphenyl oxide disulfonic acid may be presentin an amount of about 4,500 ppm.

The electrolyte of any embodiment disclosed herein may further include acorrosion inhibitor. The corrosion inhibitor may be used to helpmaintain a clean zinc surface, which in turn increases cell voltage andefficiency. Both the corrosion inhibitor and the amphotericfluorosurfactant may provide improvements in cell voltage and cellperformance. The corrosion inhibitor may enhance conductivity. Thecorrosion inhibitor may be present in the electrolyte from about 100 ppmto about 15,000 ppm, such as from about 200 ppm to about 300 ppm. In anyembodiment herein, it may be the corrosion inhibitor is present in anamount of about 150 ppm, about 200 ppm, about 250 ppm, about 300 ppm,about 350 ppm, or any range between any two of these values (includingendpoints). In any embodiment herein, the corrosion inhibitor may bepresent in an amount of about 250 ppm. With regard to the corrosioninhibitor only, the ppm amount is based upon the total weight of theelectrolyte when the corrosion inhibitor is a liquid at roomtemperature, or it is based upon the zinc weight in the anode when thecorrosion inhibitor is a solid at room temperature.

The corrosion inhibitor of any embodiment of the present technology maybe an aromatic amine polymer, indium hydroxide, polyaniline,polyethylene glycol, polypropylene glycol, lithium hydroxide, lithiumhydroxide monohydrate, lithium hydroxide hydrate, or a combination ofany two or more thereof. For example, the corrosion inhibitor mayinclude a compound of Formula (II)

wherein R⁹, R¹⁰, R¹¹, and R¹² are each independently a hydrogen,substituted or unsubstituted alkyl, substituted or unsubstitutedalkenyl, or substituted or unsubstituted cycloalkyl group; and t is100-500. In any embodiment disclosed herein, it may be R⁹, R¹⁰, R¹¹, andR¹² are each hydrogen. In any embodiment disclosed herein, it may be, tis 100-200. In any embodiment disclosed herein, it may be R⁹, R¹⁰, R¹¹and R¹² are each hydrogen and m is 100-200.

As discussed above, the corrosion inhibitor may include polyaniline. Forexample, the polyaniline may be an emeraldine polyaniline. Theemeraldine form of polyaniline may be neutral and have a high stabilityat room temperature. The polyaniline of any embodiment disclosed hereinmay be a non-acid doped form of polyaniline and not a conductive form ofpolyaniline. The polyaniline of any embodiment disclosed herein may actas a corrosion inhibitor and/or may provide other benefits that do notlimit the polyaniline to acting just as a corrosion inhibitor. Thus,referring to the polyaniline as a “corrosion inhibitor” does not limitthe polyaniline to only that particular function. For example, thepolyaniline may enhance conductivity.

As discussed above, the corrosion inhibitor may include indiumhydroxide. In any embodiment disclosed herein, the indium hydroxide maybe present in an amount from about 2,000 ppm to about 4,000 ppm basedupon the total weight of the zinc in the anode, such as from about 2,500ppm to about 3,500 ppm, or from about 2,750 ppm to about 3,250 ppm.Thus, the indium hydroxide may be present in an amount of about 2,000ppm, about 2,500 ppm, about 3,000 ppm, about 3,500 ppm, about 4,000 ppm,or ranges between any two of these values (including endpoints). Forexample, the indium hydroxide may be present in any embodiment disclosedherein in an amount of about 3,000 ppm based upon the total weight ofthe zinc in the anode.

The electrolyte may include a gelling agent. Any suitable gelling agentin the art may be used so long as it does not depart from the scope ofthe present disclosure. The gelling agent may be present in an amountfrom about 500 ppm to about 1,500 ppm, about 750 ppm to about 1,250, orabout 900 ppm to about 1,100 ppm, based upon the total weight of theelectrolyte. Thus, the gelling agent may be present in an amount ofabout 500 ppm, about 600 ppm, about 700 ppm, about 800 ppm, about 900ppm, about 1,000 ppm, about 1,100 ppm, about 1,200 ppm, about 1,300 ppm,about 1,400 ppm, or about 1,500 ppm, or ranges between any two of thesevalues (including endpoints). For example, the gelling agent may bepresent in any embodiment disclosed herein in an amount of about 1,000ppm. In any embodiment disclosed herein, the gelling agent may be apolyacrylic acid polymer, such as a cross-linked polyacrylic acidpolymer.

The electrolyte may include a polyacrylate polymer. The polyacrylatepolymer may be present in an amount from about 1,000 ppm to about 5,000ppm. This may include from about 2,000 ppm to about 4,000 ppm, or fromabout 2,500 ppm to about 3,500 ppm. Thus, the polyacrylate polymer maybe present in any embodiment disclosed herein in an amount of about2,000 ppm, about 2,500 ppm, about 3,000 ppm, about 3,500 ppm, about4,000 ppm, or ranges between any two of these values (includingendpoints). For example, the polyacrylate polymer may be present in anamount of about 2,000 ppm. By way of example, a suitable polyacrylatepolymer is a cross-linked polyacrylate polymer.

Zinc oxide may be present in an amount from about 1% to about 10%, byweight of the electrolyte. This may include about 1% to about 8%, 1% toabout 5%, about 1.5 to about 5%, or about 2 to about 5%, by weight ofthe electrolyte. Thus, the zinc oxide may be present in any embodimentdisclosed herein in an amount of about 1%, about 1.5%, about 2%, about2.5%, about 3%, about 3.5%, or about 4%, by weight of the electrolyte,or ranges between any two of these values (including endpoints). Forexample, the zinc oxide may be present in an amount of about 2%, byweight of the electrolyte. The zinc oxide may provide other benefitsthat do not limit the zinc oxide to acting just as a gas suppressingadditive, and therefore referring to the zinc oxide as a “gassuppressing additive” does not limit the zinc oxide to only thatparticular function. For example, the zinc oxide of any embodimentdisclosed herein may regulate zinc surface passivation.

The electrolyte may include potassium hydroxide. The potassium hydroxidemay be present in an amount of from about 20% to about 45%, by weight ofthe electrolyte, such as from about 25% to about 40% or from about 30%to about 35%, by weight of the electrolyte. In any embodiment disclosedherein, the potassium hydroxide may be present in an amount of about45%, about 30%, about 25%, or about 20%, by weight of the electrolyte,or ranges between any two of these values (including endpoints). Forexample, the potassium hydroxide may be present in an amount of about33%, by weight of the electrolyte.

The electrolyte may include sodium hydroxide. The sodium hydroxide maybe present in an amount of from about 20% to about 45%, such as fromabout 25% to about 40% or from about 30% to about 35%, by weight of theelectrolyte. The sodium hydroxide may be present in any embodimentdisclosed herein in an amount of about 45%, about 30%, about 25%, orabout 20%, by weight of the electrolyte, or ranges between any two ofthese values (including endpoints). For example, the sodium hydroxidemay be present in an amount of about 33%, by weight of the electrolyte.

In any embodiment disclosed herein, the electrolyte of the metal-airbattery may include a surfactant system and a corrosion inhibitor, wherethe surfactant system includes the amphoteric fluorosurfactant. Thesurfactant system may further include a gas suppressing additive. In anyembodiment disclosed herein, the surfactant system may further includeshexyl diphenyl oxide disulfonic acid, diethylenetriamine, oroctylphenoxypolyethoxyethanol, a compound of Formula (III), or acombination of any two or more thereof. Gas suppressing additives mayinclude materials such as LiOH or ZnO. In any embodiment disclosedherein, the electrolyte may include from about 500 ppm to about 20,000ppm of a gas suppressing additive. Thus, the electrolyte may include gassuppressing additives in an amount of about 500 ppm, about 600 ppm,about 700 ppm, about 800 ppm, about 900 ppm, about 1,000 ppm, about2,000 ppm, about 3,000 ppm, about 4,000 ppm, about 5,000 ppm, about6,000 ppm, about 7,000 ppm, about 8,000 ppm, about 9,000 ppm, about10,000 ppm, about 11,000 ppm, about 12,000 ppm, about 13,000 ppm, about14,000 ppm, about 15,000 ppm, about 16,000 ppm, about 17,000 ppm, about18,000 ppm, about 19,000 ppm, about 20,000 ppm, or ranges between anytwo of these values (including endpoints).

The electrolyte of any embodiment disclosed herein may include LiOH inan amount of about 500 ppm, about 600 ppm, about 700 ppm, about 800 ppm,about 900 ppm, about 1,000 ppm, about 2,000 ppm, about 3,000 ppm, about4,000 ppm, about 5,000 ppm, about 6,000 ppm, about 7,000 ppm, about8,000 ppm, about 9,000 ppm, about 10,000 ppm, about 11,000 ppm, about12,000 ppm, about 13,000 ppm, about 14,000 ppm, about 15,000 ppm, about16,000 ppm, about 17,000 ppm, about 18,000 ppm, about 19,000 ppm, about20,000 ppm, about 21,000 ppm, about 22,000 ppm, about 23,000 ppm, about24,000 ppm, about 25,000 ppm or ranges between any two of these values(including endpoints).

The metal-air battery of any embodiment disclosed herein may include acarbon dioxide scrubbing agent to improve cell-performance and life. Asthe air enters the cell, the carbon dioxide reacts with the carbondioxide scrubber, to prevent, or at least minimize, the reaction of thecarbon dioxide with alkaline components in the electrolyte or at thesurface of an air diffusion membrane. The scrubbers allow for theconductivity of the electrolyte and the cathode porosity to bemaintained for an extended period of time. The electrolyte of anyembodiment disclosed herein may be seeded with materials thatpreferentially react with dissolved carbon dioxide prior to reactionwith alkali hydroxides that are present in the electrolyte.

Illustrative carbon dioxide scrubbers include, but are not limited to,lithium hydroxide, calcium hydroxide, lithium peroxide, lithium oxide,an amine, an olivine, or other basic hydroxides.

In any embodiment disclosed herein the carbon dioxide scrubbing agentmay be used to coat the inside of the cathode can in a space whereentering air may encounter the scrubbing agent prior to contacting theanode active material (i.e. the zinc). For example, as illustrated inFIG. 1 , air reservoir 55 is a void space within the battery cell. Thecell is configured such that air enters the cell through air accessports 54 prior to contacting the diffusion layer 32. Accordingly, thecarbon dioxide scrubbing agent may be applied to an interior surface ofthe cell, within the air reservoir 55, to remove or at least mitigatecarbon dioxide as it enters the cell through the air access ports 54.The scrubbing agent may also be embedded within or deposited on any ofthe cellulose air diffusion layer 32, the cathode 42, or the porousdiffusion layer 57. The scrubbing agent may be deposited as a powder, asa film by applying it through a solvent that is later removed, or byother practical means.

In any embodiment disclosed herein, the carbon dioxide scrubbing agentsmay be added to the alkaline electrolyte. In such embodiments, thescrubbing agents are selected such that the material reactions withcarbon dioxide first, while preserving the NaOH or KOH that is presentin the electrolyte. Without being bound by theory, it is believed thatas CO₂ enters a zinc-air cell, the CO₂ can dissolve in the aqueouselectrolyte, thereby forming carbonic acid. The carbonic acid may thenreact with the scrubber prior to reaction with the NaOH or KOH presentin the electrolyte, such that the desired alkalinity of the electrolyteis maintained.

In any embodiment disclosed herein, a carbon dioxide scrubbing agent maybe included in packaging that contains a hearing aid cell (according tothe present technology) to minimize storage damage due to carbon dioxideexposure, prior to use of the cell. For example, the packaging maycontain a chamber which is intended for holding a zinc-air cell, such asa hearing aid battery, for storage or sale. The packaging may includeany of the carbon dioxide scrubbing agents as powders, coatings on thepackaging materials, or embedded within the plastics or papers that makeup the packaging and chamber forming materials.

The anode includes an anode active material, and an anode can assemblymay surround the anode active material. In any embodiment disclosedherein, the anode active material may include zinc and the anodereferred to as a “zinc anode.” In this regard, it is to be noted that,as used herein, anode “active material” may refer to a single chemicalcompound that is part of the discharge reaction at the anode of a celland contributes to the cell discharge capacity, including impurities andsmall amounts of other moieties that may be present therein. Anode“active material” does not include current collectors, electrode leads,etc., that may contain or support the zinc active material.

Physical modifications to the anode may also improve cell service life,either alone or in combination with chemical modifications noted above.For example, one can efficiently discharge cells having anadvantageously lower concentration of hydroxide ions in the electrolytethan can be used in conventional cells by reducing diffusion resistancefor the hydroxide ions. This can be accomplished, for example, byadjusting the zinc particle size distribution to provide in the anode anarrow distribution of similar zinc particle sizes, thereby enhancingporosity (diffusion paths) for the hydroxide ions. In addition toimproving diffusion properties, the particle size distributions of thisdisclosure also provide the porosity sites for the precipitation of ZnO,thereby delaying anode passivation. This approach is effective for usein the anodes of zinc air battery cells and can be used in combinationwith other improvements disclosed herein.

Suitable zinc particle size distribution is one in which at least 70% ofthe particles have a standard mesh-sieved particle size within a 100micron size range and in which the mode of the distribution is betweenabout 100 and about 300 microns. A suitable zinc particle sizedistribution includes particle size distributions meeting theabove-noted tests and having a mode of about 100 microns, about 150microns, or about 200 microns. In any embodiment disclosed herein, itmay be about 70% of the particles are distributed in a size distributionrange narrower than about 100 microns, for example about 50 microns, orabout 40 microns, or less.

The positive electrode may include a cathode can assembly 40, whichincludes a cathode can 44 and the cathode 42. An exemplary embodiment ofthe cathode 42 is best seen in FIG. 1 . An active layer 72 of thecathode 42 is interposed between the separator 74 and the porousdiffusion layer 57. Active layer 72 ranges preferably between about 50microns and about 1,250 microns thick, and facilitates the reactionbetween the hydroxyl ions in the electrolyte and the cathodic oxygen ofthe air. The separator 74 may include or consist of one or both of amicro-porous plastic membrane and a micro-porous cellulosic paper. Themicro-porous plastic membrane is about 25 microns thick and typicallycomposed of polypropylene. The paper material is 70-90 microns thickwith a basis weight of 20 to 25 g/m², and typically composed ofpolyvinyl alcohol and cellulosic material. The separator has the primaryfunction of preventing anodic zinc particles from coming into physicalcontact with the remaining elements of the cathode 42. The separator 74however, does permit passage of hydroxyl ions and water therethrough tothe cathode assembly. Here, the cathode is an air cathode and thecathode active layer includes carbon.

The side wall 47 of the cathode can 44 is joined to the bottom 46 of thecan by intermediate element 80. The outer surface of intermediateelement 80 extends, from its lower end at outer perimeter 52 of outersurface 50 of bottom 46, to its upper end which joins the outer surface58 of the side wall 47 in a generally vertical orientation. The innersurface, if any, of the intermediate element 80 is represented at thejoinder of the inner surface 48 of the bottom 46 and the inner surface56 of the side wall 47. The inner surfaces 48 and 56 may come togetherat a sharp corner, such that the inner surface of the intermediateelement is of nominal dimension. To the extent the corner material isworked in forming the corner, the corner may be work hardened, wherebythe corner structure is strengthened with respect to bottom 46 and sidewall 47 as the corner structure is formed at intermediate element 80.

In any embodiment disclosed herein, the can/housing may be formedentirely of a metal or alloy having a hydrogen overvoltage similar tothat of the cathode (as opposed to plating or cladding the can) so longas sufficient strength and ductility are available from the materialselected. Materials in addition to nickel, having such hydrogenovervoltage properties, include, for example and without limitation,cobalt and gold. In some embodiments, such materials may be coated asone or more coating layers onto the core layer by, for example, plating,cladding, or other application processes. The materials which providesufficient strength and ductility may also be used as single layermaterials in place of the composite structure. Single layer materialscomprehend CRS or other suitable material as a core layer.

In any embodiment disclosed herein, a steel strip plated with nickel andnickel alloy may be used because of cost considerations, and becausepre-plated steel strip, which generally requires no post-platingprocesses, is commercially available. The metal in the can/housing ispreferably both ductile enough to withstand the drawing process, andstrong and rigid enough, to tolerate and otherwise withstand cellcrimping and closure processes as well as to provide primary overallstructural strength to the cell/battery.

In any embodiment disclosed herein, the housing may be includenickel-clad stainless steel; cold-rolled steel plated with nickel;INCONEL® (a non-magnetic alloy of nickel); pure nickel with minoralloying elements (e.g. Nickel 200 and related family of Nickel 200alloys such as Nickel 201, etc.), all available from Huntington Alloys,or DURANICKEL® 301, available from Special Metals. For example, thehousing may be made of nickel-plated stainless steel. Some noble metalsmay also find use as plating, cladding, or other coating for can/housingmetals, including covering steel strip plated with nickel, and mildsteel strip subsequently plated with nickel after fabricating the can.

Where multiple layers are used (e.g., CRS) coated on opposing sides withnickel, the present disclosure contemplates optional additional (e.g.fourth, fifth, etc.) layers, either between the nickel and CRS, or witha nickel layer between the CRS and the additional layer(s). For example,gold, cobalt, or other excellent electrical conductor can be depositedon some or all of the outer surface of the cathode can (outside thenickel layer) after the can is drawn, or drawn and ironed. As analternative, such fourth etc. layer can be, for example, abond-enhancing layer between the CRS and the nickel.

Where the can/housing is fabricated using a typical raw materialstructure of nickel/stainless steel (SST)/nickel/NI/SST/NI as the sheetstructure, such sheet structure may be from about 0.05 mm to about 0.3mm. This may include about 0.076 mm to about 0.25 mm or about 0.1 mm toabout 0.15 mm—thus, the thickness may be about 0.05 mm, about 0.076 mm,about 0.1 mm, about 0.13 mm, or about 0.15 mm, or ranges between any twoof these values (including endpoints). For example, the thickness may beabout 0.13 mm. In any embodiment disclosed herein, it may be each of thenickel layers represents about 1% to about 10%, of the overall thicknessof the metal sheet in such 3-layer structure. This may include about1.5% to about 9%, about 2% to about 8%, about 2.5% to about 7%, or about3% to about 6.5%, of the overall thickness of the metal sheet in such3-layer structure. For example, each of the nickel layers representsabout 2% to about 4%, of the overall thickness of the metal sheet insuch 3-layer structure. In any embodiment disclosed herein, it may beeach of the nickel layers represents about 2%, of the overall thicknessof the metal sheet in such 3-layer structure.

The present invention, thus generally described, will be understood morereadily by reference to the following examples, which are provided byway of illustration and are not intended to be limiting of the presentinvention.

EXAMPLES

Example 1. Size 312 cells of the present technology with a total ventarea of 0.0498 mm² were prepared using a zinc anode and an aqueouselectrolyte that included (by weight of the electrolyte) 31.5% potassiumhydroxide, 10,000 ppm of an amphoteric fluorosurfactant, 1.5% lithiumhydroxide, 2% zinc oxide, and 1,000 ppm polyacrylic acid. Comparative“standard” cells were likewise prepared but with the exception that thestandard cells did not include an amphoteric fluorosurfactant and thatthe total vent area was 0.1329 mm². The cells were discharged accordingto the ANSI/IEC test 10/2 mA at 80% RH (relative humidity), where thecells of the present technology exhibited an improvement in capacity ofabout 15% over the comparative “standard” cells.

Example 2. Size 13 cells of the present technology with a total ventarea of 0.0998 mm² were prepared using a zinc anode and an aqueouselectrolyte that included potassium hydroxide, the amphotericfluorosurfactant of Example 1, lithium hydroxide, and the polyacrylicacid of Example 1 in the same amounts as for the electrolyte ofExample 1. Comparative “standard” cells were likewise prepared but withthe exception that the standard cells did not include an amphotericfluorosurfactant and that the total vent area was 0.1295 mm². The cellswere discharged according to the ANSI/IEC test 12/3 mA at 80% RH(relative humidity), where the cells of the present technology exhibitedan improvement in capacity of about 7% over the comparative “standard”cells (FIG. 2 ).

Example 3. Size 312 cells of the present technology with a total ventarea of 0.0660 mm² were prepared using a zinc anode and an aqueouselectrolyte that included potassium hydroxide, the amphotericfluorosurfactant of Example 1, lithium hydroxide, and the polyacrylicacid of Example 1 in the same amounts as for the electrolyte ofExample 1. Comparative “standard” cells were likewise prepared but withthe exception that the standard cells did not include an amphotericfluorosurfactant and that the total vent area was 0.0869 mm². The cellswere discharged according to the ANSI/IEC test 10/2 mA at 80% RH(relative humidity), where the cells of the present technology exhibitedan improvement in capacity of about 13% over the comparative “standard”cells (FIG. 3 ).

Example 4. Size 312 cells of the present technology with a total ventarea of 0.0660 mm² were prepared using a zinc anode and an aqueouselectrolyte that included potassium hydroxide, the amphotericfluorosurfactant of Example 1, lithium hydroxide, and the polyacrylicacid of Example 1 in the same amounts as for the electrolyte ofExample 1. Comparative “standard” cells were likewise prepared but withthe exception that the standard cells did not include an amphotericfluorosurfactant and that the total vent area was 0.0869 mm². The cellswere discharged according to the ANSI/IEC test 10/2 mA at 20% RH(relative humidity), where the cells of the present technology exhibitedan improvement in capacity of about 4% over the “comparative” standardcells (FIG. 4 ).

Example 5. To further illustrate the contributions of the electrolyteitself to the performance of the batteries of the present technology,three aqueous electrolytes were generated and assessed as follows. Thethree electrolytes were:

-   -   (1) an aqueous electrolyte including 33% potassium hydroxide (by        weight of the electrolyte) and 2% zinc oxide (by weight of the        electrolyte);    -   (2) an aqueous electrolyte including 33% potassium hydroxide (by        weight of the electrolyte), 2% zinc oxide (by weight of the        electrolyte), and 7,500 ppm of a carboxylated amine surfactant;        and    -   (3) an aqueous electrolyte of the present technology, including        33% potassium hydroxide (by weight of the electrolyte), 2% zinc        oxide (by weight of the electrolyte), and 10,000 ppm of an        amphoteric fluorosurfactant.        Cathode performance resulting from use of an electrolyte was        tested independently from anode performance by placing a pure        zinc reference electrode in the solution close to the cathode        (note: the same distance from the cathode was used for all        tests), where the cathode had unlimited air access on one side        and was exposed to the electrolyte on the other side (“cathode        half cell”). Subsequently, a current draw of 1 mA/cm² and 5        mA/cm² were applied to the cathode and the potential versus the        pure zinc reference was recorded for each electrolyte described        above. As illustrated in FIG. 5 , the aqueous electrolyte of the        present technology (3) exhibited improved behavior with less        voltage drop with the same current draw over aqueous        electrolytes (1) and (2).

Example 6. To further illustrate the difference between the presenttechnology and prior art, a large number of size 13 cells of each typewere tested for limiting current at 1.15V and 0.9V. It is observed thatthe ratio of limiting current at 1.15V to limiting current at 0.9V isgreater for the present technology than for commercial cells. FIG. 6illustrates the ratio for both cell types. To examine in further detail,the limiting current at 1.15V was plotted against limiting current at0.9V for multiple cells of each type. It is observed that both limitingcurrents vary from cell to cell, but are correlated with each other,having a relatively constant ratio that is a characteristic of thepresent technology vs. commercial cells.

Example 7. Size 13 cells were discharged at constant current, shown inFIG. 8. The cell of the present technology has limiting current at 0.9Vof 12 mA. When discharged at a rate of 4 mA, or one-third of thelimiting current at 0.9V, it provides a voltage greater than 1.2Vthrough the majority of the discharge. This is particularly importantsince many practical devices send “low battery” warnings to the userwhen the voltage drops below about 1.1V.

When the cell of the present technology is discharged at 6 mA, or halfof the limiting current at 0.9V, it is still able to provide voltagegreater than 1.17V through the first half of discharge.

By comparison, a commercially available cell with limiting current at0.9V of 18 mA, discharged at 6 mA, is reflecting a current drain equalto one-third of the limiting current at 0.9V. It provides lower voltagethan the present technology. In addition, the higher limiting currentwill lead to more moisture and carbon dioxide transport, affecting thecell negatively, particularly in lower-rate conditions in which the timeof discharge is longer.

Example 8. In another test, the present technology is found to enableeven smaller vent areas. Size 312 cells of the present technology withthree different total vent areas from 0.0330 mm² to 0.0869 mm² wereprepared using a zinc anode and an aqueous electrolyte that includedpotassium hydroxide, the amphoteric fluorosurfactant of Example 1,lithium hydroxide, and the polyacrylic acid of Example 1. The cells weredischarged according to the ANSI/IEC test 10/2 mA at 50% RH (relativehumidity) and the ANSI/IEC test 5/2 mA at 50% RH, where the cells of thepresent technology exhibited no statistical difference in capacity ofover the range of tested total vent areas (FIG. 9 , FIG. 10 ).

Example 9. Size 13 cells of the present technology with three differenttotal vent areas in the range of 0.0499 mm² to 0.1295 mm² were preparedusing a zinc anode and an aqueous electrolyte that included potassiumhydroxide, the amphoteric fluorosurfactant of Example 1, lithiumhydroxide, and the polyacrylic acid of Example 1. The cells weredischarged according to the ANSI/IEC test 12/3 mA at 50% RH (relativehumidity) and the ANSI/IEC test 5/3 mA at 50% RH, where the cells of thepresent technology exhibited no statistical difference in capacity ofover the range of tested total vent areas (FIG. 11 , FIG. 12 ).

While certain embodiments have been illustrated and described, it shouldbe understood that changes and modifications can be made therein inaccordance with ordinary skill in the art without departing from thetechnology in its broader aspects as defined in the following claims.

The embodiments, illustratively described herein may suitably bepracticed in the absence of any element or elements, limitation orlimitations, not specifically disclosed herein. Thus, for example, theterms “comprising,” “including,” “containing,” etc. shall be readexpansively and without limitation. Additionally, the terms andexpressions employed herein have been used as terms of description andnot of limitation, and there is no intention in the use of such termsand expressions of excluding any equivalents of the features shown anddescribed or portions thereof, but it is recognized that variousmodifications are possible within the scope of the claimed technology.Additionally, the phrase “consisting essentially of” will be understoodto include those elements specifically recited and those additionalelements that do not materially affect the basic and novelcharacteristics of the claimed technology. The phrase “consisting of”excludes any element not specified.

The present disclosure is not to be limited in terms of the particularembodiments described in this application. Many modifications andvariations can be made without departing from its spirit and scope, aswill be apparent to those skilled in the art. Functionally equivalentmethods and compositions within the scope of the disclosure, in additionto those enumerated herein, will be apparent to those skilled in the artfrom the foregoing descriptions. Such modifications and variations areintended to fall within the scope of the appended claims. The presentdisclosure is to be limited only by the terms of the appended claims,along with the full scope of equivalents to which such claims areentitled. It is to be understood that this disclosure is not limited toparticular methods, reagents, compounds compositions or biologicalsystems, which can of course vary. It is also to be understood that theterminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting.

In addition, where features or aspects of the disclosure are describedin terms of Markush groups, those skilled in the art will recognize thatthe disclosure is also thereby described in terms of any individualmember or subgroup of members of the Markush group.

As will be understood by one skilled in the art, for any and allpurposes, particularly in terms of providing a written description, allranges disclosed herein also encompass any and all possible subrangesand combinations of subranges thereof. Any listed range can be easilyrecognized as sufficiently describing and enabling the same range beingbroken down into at least equal halves, thirds, quarters, fifths,tenths, etc. As a non-limiting example, each range discussed herein canbe readily broken down into a lower third, middle third and upper third,etc. As will also be understood by one skilled in the art all languagesuch as “up to,” “at least,” “greater than,” “less than,” and the like,include the number recited and refer to ranges which can be subsequentlybroken down into subranges as discussed above. Finally, as will beunderstood by one skilled in the art, a range includes each individualmember.

All publications, patent applications, issued patents, and otherdocuments referred to in this specification are herein incorporated byreference as if each individual publication, patent application, issuedpatent, or other document was specifically and individually indicated tobe incorporated by reference in its entirety. Definitions that arecontained in text incorporated by reference are excluded to the extentthat they contradict definitions in this disclosure.

The present technology may include, but is not limited to, the featuresand combinations of features recited in the following letteredparagraphs, it being understood that the following paragraphs should notbe interpreted as limiting the scope of the claims as appended hereto ormandating that all such features must necessarily be included in suchclaims:

Other embodiments are set forth in the following claims.

What is claimed is:
 1. A battery comprising an air cathode, an anode, anaqueous electrolyte, and a housing, wherein: the housing comprises oneor more air access ports defining a total vent area; the batteryexhibits a cell limiting current at 0.9V and a cell limiting current at1.15V; the ratio of cell limiting current at 1.15 V to cell limitingcurrent at 0.9V is greater than about 0.6; and the aqueous electrolytecomprises an amphoteric fluorosurfactant.
 2. The battery of claim 1,wherein the ratio is greater than about 0.75.
 3. The battery of claim 1,wherein the ratio is from about 0.6 to about 0.9.
 4. The battery ofclaim 1 having a nominal diameter of about 8 mm and a nominal height ofabout 5.4 mm.
 5. The battery of claim 1 having a nominal diameter ofabout 8 mm and a nominal height of about 3.6 mm.
 6. The battery of claim1, wherein the battery has a nominal external volume from about 180 mm³to about 270 mm³.
 7. The battery of claim 1, wherein the battery has anominal electrode interfacial area that is about 35 mm².
 8. The batteryof claim 1, wherein the total vent area is from about 0.030 mm² to about0.13 mm².
 9. The battery of claim 1, wherein the cell limiting currentat 1.15 V is about 4 mA to about 15 mA.
 10. A battery comprising an aircathode, an anode, an aqueous electrolyte, and a housing, wherein: thehousing comprises one or more air access ports defining a total ventarea; the battery has an interfacial surface area between the anode andcathode; a ratio of vent area to interfacial area is about 3×10⁻³ orsmaller, provided that when the battery is a size 13 battery then theratio is about 2.4×10⁻³ or smaller; and the aqueous electrolytecomprises an amphoteric fluorosurfactant.
 11. The battery of claim 10,wherein the ratio is from about 1.0×10⁻³ to about 3.0×10⁻³, and whereinthe battery is not a size 13 battery.
 12. The battery of claim 10,wherein the ratio is from about 1.0×10⁻³ to about 2.4×10⁻³.
 13. Thebattery of claim 10, wherein the ratio is from about about 1.4×10⁻³ toabout 3.0×10⁻³, and wherein the battery is not a size 13 battery. 14.The battery of claim 10 having a nominal diameter of about 8 mm and anominal height of about 5.4 mm.
 15. The battery of claim 10 having anominal diameter of about 8 mm and a nominal height of about 3.6 mm. 16.The battery of claim 10, wherein the battery has a nominal externalvolume from about 180 mm³ to about 270 mm³.
 17. The battery of claim 10,wherein the battery has a nominal electrode interfacial area from about25 to 50 mm².
 18. The battery of claim 10, wherein a total vent area isfrom about 0.030 mm² to about 0.115 mm².